Interlocking switch for electric heaters



Oct. 17, 1950 A. J. HUCK 2,526,234

INTERLOCKING SWITCH FOR ELECTRIC HEATERS Filed Jan. 20, 1947 3 Sheets-$heet 1 3/? 32 INVENTOR. J10 112 flZ/redJ/fzwl,

A TTORNEYS.

Oct. 17, 1950 A. J. HUCK 2,526,234

INTERLOCKING SWITCH FOR ELECTRIC HEATERS Filed Jan. 20, 1947 s Sheets-Sheet 2 INTER LOCKING SWITCH SETTING COMBINRTIONS Commune LEFT BURNER RIGHT BURNER ToTnL Wins 1 DFF OFF 00 00 2 Low HIGH lb 00 3 OFF HIGH I2 00 4 MED MED lb 00 5 L MED 12 oo 6 OFF MED a DD 7 mau LOW lb 00 g MED LOW I2 00 9 LOW LOW a 00 10 OFF Low 4 00 F 6 11 man OFF 12 00 g; 12 MED OFF a 00 .I 7 F 12 LOW oFF 4 oo 4 MEDIUM WATTASE INVENTOR. JZ/reJJHuJ/Z ATTORNEYS.

Oct. 17, 1950 A. J. HUCK 2,526,234

INTERLOCKING SWITCH FOR ELECTRIC HEATERS Filed Jan. 20', 1947 3 Sheets-Sheet 3 VWM-- E L! 60 (0) E I 100 2 25; 44 1a if; 11a 96 2 -66 INVENTOR. dz 5: fl'lfradJ/fiwlq BY 6; M

. ATTORNEYS.

mum wattage rating.

Patented Oct. 17, 1950- INTERLOCKING SWITCH FOR ELECTRIC HEATERS Alfred J, Huck, St. Louis, M0,, assignor to Knapp- Monarch Company, St. Louis, Mo., a corporation of Delaware Application January 20, 1947, .Serial No. 723,069

My present invention relates to a switch for controlling a plurality of electrical appliances such as-stove plates or the like, wherein parts of the switch are so interlocked mechanically that a maximum wattage is not'exceeded in any possible combination of energization for the different appliances, yet each one under certain conditions can be energized with more than its proportionate share of current.

One object of the invention is to provide a switch of this general character which is simple in construction and can be readily fabricated, the assembled switch being comparatively inexpensive and simple to connect into circuits of the appliances controlled, thereby minimizing the number f circuit connections between the switch structure and the heating elements.

Another object is to provide a plurality of switch units, one for each appliance, the switch units being interlocked mechanically as b means of switch operating cams so that upon adjustment of the switch structure to a pos tion for maximum current in one appliance, there will be no possibility of more thana' predetermin d lesser amount of current available for the other appliance or appliances so that the total wattage drain on the supplywires is within a safe maxi- A further object is to provide a switch structure designed specifically for two heating units as in an electric stove or the like, wherein high, medium and low heats can be'provided for one burner; and high, medium and .low heats may also be provided for the other burner,

.the switch structure being so designed as to permit no more than a, high and a medium combination of the two burners as a maximum availa le current supply for both burners and prevent any possibility of high heat to both burners or high heat to one and medium Another additional bject is to provide a modi- .fied arrangement for operating a single neon or other type of electric pilot light for each burner, together with a balla t coilarrangement which permits the single light to be illuminated with three different degrees of intensity, thus simpli- 6 Claims. (Cl. 2 1920) fying the pilot light arrangement and wiring due to the use of one bulb instead of two.

g With these and other objects in view, m invention consists of the construction, arrangement and combination of the various parts of my device whereby the objects contemplated are attained, as hereinafter more fully set forth,

pointed out in my claims and illustrated in the accompanying drawings, wherein:

Fig. l is a front elevation of an interlocking switch structure embodying my present invention showing it mounted on the front wall of a stove, or the like, showing in dotted lines the pilot lights back of the front wall, and showing a cam for the medium wattage elements in dotted lines.

Fig. 2 is a plan view of Fig. 1 showing the front wall of the stove in section.

Fig. 3 is a sectional view on the line 3-3 of Fig. 2 showing the dotted cam of Fig. '1 in full lines and a second cam in dott d lin s, the second cam being for the low Wattage elements.

Fig. 4 is an electro-diagrammatic view showing the switch structure, the pilot lights and the left and right hand burners connected together and to a current supply cord.

Fig. 5 is a layout view of the back cam for controlling the low wattage elements and show ing the relationship of notches of the cam to numbered stations on the cam.

Fig. 6 is a simi ar layout view of the front cam for controlling the medium wattage elements.

Fig.7 is a, chart showing the different setting combinations of the interlock ng switch, heating conditions of the left and right burners for each a combination, and the total number of watts for each combination.

Fig. 8 is a view similar to Fig. 3 showing the switches in closed rather than open po ition.

the reference numeral 20 to indicate a shaft.

The shaft 20'is journaled in a front plate 22 and a'rear plate 24 of a Switch frame, the frame having side plates '26 and 28,.

The switch frame 22, 24, 26 and 28 maybe mounmd on a front wall 30 of an electrical appliance such as a stove, as by means of screws 32 (see Fig. 2). The scre s are cover d by a panel .34 having a substantially circular dial porfor the left burner.

3 tion 36. The panel 34 is held in position by tubular sleeves 38 and lock nuts 40, each tubular sleeve having on its outer end an indicator lens 42.

The side plates 26 and 28 of the switch frame are provided with inturned flanges 44 on which are mounted two contact brackets 46 for the left and right hand burners which are indicated as LB and RB res ectively in Fig. 4.

A supply cord having wires 48 and 50, and a plug 52 for plug ing into a service outlet is provided, the wires being connected with terminals 54 and 56 respectivel of a terminal block 58. The terminal block is suitably mounted on the stove or a liance. A wire 60 then connects the terminal 54 with both brackets 46 which are shown in the exploded view of Fig. 4 as four brackets.

The l ft burner LB has a p ir of heating elements LL an LM. These reference characters indicate low and medium heating elements High heat is had by energi"ing both heating elements.

For the ri ht burner RB a right low eler ent RL and a right medium elemen RM are shown. For the va ious heating e ements four switch blades LL, LM'. RL' and RM are provided, the switch blades be ng likewise mounted on the fla nges 44 of the switch frame, The switch b ades and also the brackets 46 are mount d on the e flanges as by rivets 69. th ough suitable in ua ion plat s 64. t e p tes being secured to I provide a back cam B having lobes and depressions as sho n in Figs. 3, 4 and 5. For operating the sw tch b a es LM' and RM I provide -a front cam F having lobes and depres ions as sho n by dott d li s in Fi s. 1 a d 3,. and in Figs.

4 and 6. The various lob s are adapted to coact with elbows 80 of the switch blades to separate the movable contacts 82 carried thereby from the stationary contacts 84 of the brackets 46 as 1 shown in Fig. 3. When the cam are adju ted to a position where the depressions thereof coact wi h the elbows 80, then the switches are adapted to be closed as shown in Fig. 8.

The cams have been divided into 26 stations, I to I3 inclusive, and I' to similarly divided into 26 stations corresponding .thereto. The order of rotation in Fig. 1 is reversed relative to that in Figs. and 6 because the stations in Fig. 1 are for a stationary dial, whereasthe stations in Figs. 5 and 6 are for rotating cams as will hereinafter become obvious.

The cams B and F are mounted on the shaft 20 for rotation therewith and for this purpose the cams (which are preferably made of insulation material such as fibre or the like) are provided with central openings 86 having tongues 88. The tongues 88 enter a keyway 90 of the shaft 20 so that the cams are non-rotatable relative to the shaft when threaded thereon. The cams are re- --tained'on the shaft together with an indexing disc 92 by means of a lock nut 94 and a. plurality I3 inclusive as shown. in Figs. 4, 5 and 6. The dial 36 in Fig. 1 has been of spacer sleeves 96, 98, I00 and I02 as shown in Fig. 9. The cams, indexing disc, sleeves and nut constitute a rotor assembly. The spacer sleeve 96 bears against a flange I04 of the shaft 20, and the sleeve I02 is shouldered to pass through the plate 24. A cupped spring washer I06 takes up end play and engages the flange I04 with a bearing I08 in the front plate 22 of the switch frame.

The front end of the shaft 20 extends through openings in the front wall 30 of the appliance, see Fig. 2, and the panel 34, and a control knob H0 is mounted thereon. The knob II 0 has a pair of stop pins I I2 (see Fig. 1) to engage 2. Stationary stop pin II4 of the panel 34 thereby limiting the shaft 20 to slightly less than of rotation, the knob being shown in its counterclockwise position in Fig. 1.

The indexing disc 92 has a notched periphery, there being a total of 26 notches, although a disc can be made in a. 180 sector with only 13 notches. For coaction with these notches a detent roller 1 I6 is provided (see Fig. 3) which is mounted on a pin II8 carried by an arm I20. The arm I20 is pivoted at I22 to the switch frame and a leaf spring I24 is anchored to the switch frame as at I26 for biasing the arm I20 clockwise for the roller H6 to engage in the notches 0f the indexing disc, thereby definitely positioning the switch at the various stations thereof.

Mounted on each sleeve 38 is a. pilot light bracket I28 and supported thereby are pilot lights LLP and LMP for the left burner, and RLP and RMP for the right burner. The lights are connected in parallel to the heating elements LL, LM, RL and RM respectively with a common connection between them to the wires I6 and I8, all as shown by dotted lines in Fig. 4. These wires have not been given reference numerals as it is believed the circuit is clear Without referrin specifically to them in the description of the operation of the device.

Referring to Fig. 5, the 13 stations on the left half of the cam B are provided withvarious lobes and depressions which are designed for operating the left burner low heating element LL through the medium of the switch blade LL. The stations I and I3 on the right half of the cam have lobes and depressions for operating the right low heating element RL through the medium of the switch blade RL. Similarly the stations I and I3 of the cam F in Fig, 6 operate the switch blade LM, and the stations I to I3 operate the switch blade RM. The depressions are so located at the different settings I to I3 for the upper point of the knob H0 in Fig. 1 that there will be different energization combinations for 'the right burner that does not exceed 1600 watts is off for the left burner. This is position 3. Positions 4. 5 and 6 are for medium settings on the right burner, and with this setting the medium setting of the left burner also is permitted as in position 4, since both the medium heating elements are 800 watts each. The cams have been so designed that there m pos'sibilityof a high for the left burner when there is a "me dium for the right burnerorvice v'er'sa;

When the rightburner is on low, then high is permitted in the left burner as at position I,

left burnera This'is accomplished by positions I I, I2, and I3 as indicated on the chart in Fig. 7;

It will be noted that the total wattage of any combination does not exceed 1600, yet with each of high, medium, low and off on the right burner there can be had low or off on the left burner. When there is medium on the right burner, medium can also be had on the left burner. Thus by designing the cams B and F so that there is no potsibility of two-highs, or a high and a medium, the maximumcurrent drain on the wires 48 and 50 at any timedoe's not exceed 1600 watts whereas both burners at high heat would require 2400 watts, or one at high and the other watts. a I

The foregoing description discloses a comparatively simple mechanical interlock between a pair I age The construction is such'that it requires no complicated wiring connections, there being but one switch for each heating element involved and no necessity of running one wire to several different connections. 1 1

Considering the cams L and R in Figs. 5 and 6, it will be noted that at stations I and I the cams have lobes, and that at 2 and? the cam B'has depressions, whereas the cam F at station 2' has a lobe and at station 2' a depression. This causes all .four of the switch blades to be inthe open circuit positions of Fig." 3 when the knob I I0 is at the off position (stations I and I in Fig. 15 whereas when it is moved c ockwise to station 2-2 the switch blade LL, RL' and are in the depreisi'ons at stations land 2' of Fig. 6 respectively, thus energizing the low heating element LL of the'left burner and both of the heating elements RL and RM of the right'burner for high heat. This is' indicated on the chart in Fig. 7 and similarly the other low, medium 1 and high heating combinations can betraced out by comparing the chart with the depressions of the cams at the various stations correspondthe purpose of preventing any accidental closure.

of certain contacts that would give a medium and high, or high'and high combination of heating element energizations. In other words, there is a gap between the positions determined by the detent mechanism where all contacts are open to. avoid any possibility of overlapping of contacts ;.that. might momentarily mg combination with the" low of the rightat medium would require '2000 6. throw a load greater than 1600 watts on the line and result in a blown fuse.

With respect to the pilot lights LMP, LLP, RMP and RLP, they are energized when their respective heating elements LM', LL, RM and RL are energized so that the operator can determinewhether the burners are energized for low, medium or high heat without referring to the:

dial 36. The pilot lights LMP and eMP are high-- er candle power than the lights LLP and RLP, so that medium heat can be distinguished from; low heat because of the greater brightness of the lights. When. however, both of the low heat and the medium heat pilot lights are energized then a third degree of light intensity is observable through: the lens 42 and this degree is greater than either'tlie low heat light or the medium heat light when they are energized independently. I

It will be noted that "he pilot' lights LLP and BL? are farther away from the lens 42 than the pilot lights LMP and RMP. This permits the use of pilot bulbs all of the same candle power as distingui-shed: from two different candle powers as outlined in the last paragraph. This arrangement is much better for commercial production because only one type of bulb need besupplied, handled and inserted during factory assembly. The low indicating pilot bulbs being spaced farther from the lens than the medium pilot bulbs insures a lower'degr'ee of illumination for low indication than for medium indication at the lens 42 and the net effect is the same on the lens as when bulbs of different wattages or candle powers are used for the two different indications.

The use of the pilot lights of course is optional I as dial 36 gives an'indication as to the setting of each burner and the dial is so arranged that the upper end of knob H0 in Fig. 1 can be used to quickly select high, medium or low" heats for the right burner; whereas the lower end of the knob then indicates what possible heat or adjustment to off position can be had for the left hand burner for any one of the high, medium or "low heats at the right burner.

While I have described an arrangement wherein the cam B is for low wattage and the cam F is for medium Wattage, an alternative arrangement can be provided whereby the back cam B controls the low and medium heating ele ments of the left burner, that is, controls LL and LM; and the front cam F controls the low and medium. heating elements RL' and RM tions of the other burner (as described in this paragraph).

In Fig. 10 I show a modified construction wherein a single pilot light LP is provided for the left burner and RP for the right burner. The heat- :ing elements are the same as in the previous flgures and accordingly bear the same reference numerals. Switch blades and wires of the circuit corresponding to-those in Fig. 4 are also shown. By providing the pilot lights LP and RP of neon type, ballast resistors I29 and I39 may be connected as shown so that at low settings 'for the interlocking switch the high ballast resistance I28is in circuitwiththe light, whereas at the medium setting a medium ballast I30 is in the neon light circuit. At a high setting both ballasts are in parallel so as to give a low resistance and consequently a high illumination. Thus with one light for each burner, three different degrees of illumination are possible with three different degrees of energization at each burner.

The pilot lights LP and RP may be of small wattage filament typ instead of neon lights, and the ballast resistors 128 and I39 would be accordingly of somewhat lower resistance value to secure the desired results. The arrangement shown in Fig. has the advantage of using half as many pilot lights as the arrangement shown in Fig. 4, and somewhat simplifies the wiring.

From the foregoing description it will be obvious that I have provided an interlocking switch for stoves and the like, wherein it is possible to energize one burner at a higher wattage than half the available wattage for two burners. The switching arrangement is such that there is no possibility of energizing the burners so that wattage exceeds a pre-determined degree such as 1600 watts. Ordinarily two burners could be provided having a wattage rating of only 800 watts each and no interlocking of two switches is required. This is not always adequate, however, to do a good cooking job.

With my arrangement 1200 watts is available on one burner if the cooking requirements are such as to need this high a heat. The total wattage value of 1600 has been used as this is the maximum safely allowable on a ampere fuse such as commonly installed in house wiring circuits. The wattage r lationship of course, can be increased or decreased, and varied considerably within the scope of my invention. Two burners have been shown merely by way of illus tration, whereas three or more appliances may be controlled by a similar switch having additional cams and switch blades.

The construction and assembly of the switch is comparatively simple and by making the cams of the proper shapes to start with there is no subsequent problem of proper connection of wires to a plurality of switch blades as in other types of switches. One wire to each switch blade is all that is required, aside from the common wires leading to the heating elements and to the brackets 46. When once wired properly, then the switch cams automatically take care of all of the combinations as set up in Fig. 7. The key tongues 88 on the cams F and B insures proper alignment of the cams in relation to each other. and in relation to the detent disc 92 which has a similar keying arrangement. The knob H0 is also keyed properly on the shaft so that the cams rotate through their range of positions slightly less than 180 as limited by the stop pins H2 and H4.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope without sacrificing any of the advantages thereof.

I claim as my invention: 7

l. A switching system comprising a pair of appliances each having a low and a medium heating element, a shaft, a pair of cams connected thereto to operate as a unit, a pair of switches operated by each of said cams, two of said switches being provided for the low and medium heating elements of one of said appliances and the other two of said switches being provided for the low and medium heating elements of the other of said appliances, said shaft being adjustable to positions for closing said switches in different combinations which combinations include in one position of the shaft the low heating element switches for both appliances, in another position of the shaft the low heating element switch for one appliance and the medium heating element switch for the other appliance, and in still an other position of the shaft the low heating element switch only of one appliance when both the low and medium heating element switches of the other appliance are energized.

2. A switching system of the character disclosed comprising a pair of electric burners each having a low and a medium heating element, four switches only electrically connected with said low and medium heating elements of said pair of burners, two cams on one shaft for operating said switches, said cams in one position effecting closure of three of said switches to energize the low heating element of one burner and the low and medium heating elements of the other burner, said cams in a second position effecting closure of two of said switches to energize the medium heating element of each burner, said cams in a third position effecting closure of two of said switches to energize the low heating element of one burner and the medium heating element of the other burner, said cams in a forrth positon effecting closure of two of said switches to energize the low heating element of each burner, said cams in a fifth position effecting closure of only one of said switches to energize the low heating element of one burner, said cams in a s xth po-ition effecting closure of two of said switches to energize the low and medium heating e ements of only one of said burners, and said cams in a seventh position effecting closure of one of said switches to energize the medium heating element of only one of said burners, said cams in al enumerated positions having their switch operating lobes so related as to prevent energization of both l cating elements ofone burner when both heating elements of the other burner are energized.

3. An interloc ing switching system comprising a pair of electrical appliances each hav ng a low heating element and a medium heating ele ment, a single switch only for each of said four heating elements, and cam mechanism comprising two cams on one shaft or opening and closing said switches in a combinat on which in one position of the cams closes three of said switches to energize only the low heating element of one appliance when both heating elements of the other appliance are energized to provide high heat, said cams being shaped to prevent the medium heating element of one appliance being energized when both heating elements of the other appliance are energized.

4. A switching system comprising four switches, a pair of burners each having a low and a medium heating element, a pair of cams operable as a unitary structure for operating said switches, said cams in one position closing three of said switches to energize both the low and medium heating elements of one burner and simultaneously therewith only the low heating element of the other burner, in another position closing two of said switches to energize the low or medium heating element of one burner and simultaneously therewith the medium heating element of the other burner or in still another position closing two of said switches to energize the low heating elements of both burners, said cams being so shaped as to prevent the low and medium heating elements of both burners being simuitaneously energized.

5. In an interlocking switching system, a pair of heating elements each having a low section and a medium section, a single switch for each of said two sections, and a pair of simultaneously rotatable cams for said switches to close different pairs of them selectively in different positions of the cams. to energize the low section of one heating element and the medium section 1 of the other heating element, to close a different pair of said switches to effect energization of the medium sections of both heating elements, or closing different banks of three of said switches to energize both sections of one heating element but the low section only of the other heating element, said cams being so shaped as to prevent both switches for each heating element being closed at the same time.

6. In a switching system, four single normally closed switches, two burners each having a low heating element and a medium heating element, said switches being electrically connected one with each heating element and each having a switch blade, two cams connected together for simultaneous rotation, one cam for each for operating two of said switches, said cam means having notches receiving said switch blades to close said switches, said notches being arranged in circumferentially spaced relation around the'fperiphery of said cam means to effect closure in one position thereof of two of said switches to energize the medium heating element for both burners simultaneously or at anotherposition thereof closing three of said switches for energizing the low heating element oi'one burner and the low and medium heating elements of the other burner,

said cams being shaped to prevent simultaneous energization of allfour of said heating elements.

ALFRED J. HUCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,359,889 Gumaer Nov. 23, 1920 1,678,856 Forshee July 31, 1928 1,925,834 Gates Sept. 5, 1933 1,943,310 Heise Jan. 16, 1934 2,015,624 Griswold Sept. 24, 1935 2,085,217 Hart June 29, 1937 2,101,430 Goldbert et a1 Dec. 7, 1937 2,151,782 Lockwood Mar. 28, 1939 2,177,281 Lockwood Oct. 24, 1939 2,263,420 Hammell Nov. 18, 1941 2,317,967 'I'uttle Apr, 27,- 1943 2,350,078 Smith May 30, 1944 

